Well there's a clue - the ignition coil melts - so presumably the conductor that feeds the coil and melts the loom is carrying too much current.
But the ignition coils is pulsed - once for each spark - it should not take a permanent high current and enough to melt things.
So - whatever it is on your lawn tractor that sends pulses to the coil is defective - it's sending permanent current.
I know nothing of lawn mowers - I just guess.
Good Luck..., April 2017
